Most syringes used today for medical or laboratory purposes are sold as disposable items intended to be used only once. Disposal of such syringes poses a potential safety hazard for the individuals who use the syringes as well as for those who dispose of them. With the onset of AIDS, the concern for infection due to accidental needle sticks from used syringes has increased and a number of different devices have been proposed to minimize the possibility of spreading infectious disease due to accidents of this type.
One approach to this problem is to provide a retractable shield which, after the syringe has been used, can be pulled to an extended position where it covers the needle, making it difficult for an individual to accidentally contact the needle. A common feature of such constructions is that when the shield is pulled to its extended position, it is locked so that it cannot be retracted (thus exposing the needle) except by the application of extraordinary force to the shield.
A number of such constructions have been proposed to satisfy the general requirement that the needle be permanently covered after the syringe has been used. Some of these constructions involve twist-to-lock mechanisms and, in others, locking occurs automatically when the shield is fully extended. These known devices satisfy many of the functional requirements of a needle shield but require, in many cases, modification of the standard syringe construction. This is highly undesirable for many syringe manufacturers because of the sizable investment they may have already made in their existing molding equipment for producing the syringes.
Moreover, certain operational problems arise when a shield is incorporated into a syringe. For example, since the shield, when it is retracted, essentially covers the barrel of the syringe, it is desirable to be able to insert and remove a needle while holding onto the shield alone. This involves twisting and pushing (or pulling) the needle to place it on (or remove it from) the luer and can be awkward with some known constructions.
Further, constructions have been proposed which include an opening or slot in the side of the shield. This is undesirable because the needle can extend through the opening if the shield is deflected in the extended position.
Those devices which lock in response to axial movement to the extended position, (i.e., without any rotation) also have certain inherent drawbacks. The major drawback to this type of device is that the incidence of unintentional and irreversible locking is greater with such devices than with those devices which require rotation to lock.
Other proposed devices have included open ended shields which may not block access to the needle point by small fingers.
Accordingly, it is an object of this invention to provide a protective shield of the type described which can be added at minimal expense to standard syringes.
Another object of the invention is to provide a relatively inexpensive protective shield which satisfies the functional requirements of a needle shield and includes none of the drawbacks mentioned above.
Another object is to provide an extendable needle shield for a syringe which performs all of the necessary functions of such a shield and which is particularly well suited to an automated process of manufacture.
A further object of the invention is to provide an extendable needle shield for a standard syringe which is improved both from the points of view of functional utility and cost of manufacture.
A still further object is to provide an inexpensive method of assembling a protective shield and syringe.